The study of the basic electron transport mechanism through molecular systems has been made accessible by fabrication...
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The study of the basic electron transport mechanism through molecular systems has been made accessible by fabrication techniques that create metallic contacts to a small number of organic molecules. In my talk, I will discuss some of the groundbreaking discoveries such as the measurement of the conductance through a single molecule using a break junction, the demonstration of molecular diodes/transistors, and molecular-scale systems that show reversible switching behavior. Despite these exciting discoveries new theoretical and experimental studies show that molecular devices are extremely sensitive towards the nature and quality of the contacts. Questions such as: (i) what does the contact look like, (ii) is the contact changed by the electronic measurement, (iii) is the contact stable over time and as a function of temperature need to be answered. It has become necessary to spend time and research efforts on the characterization of metal-molecule contacts. In spite of great efforts, we still understand very little about the electron-transfer process through molecular junctions. Often, we cannot even draw the energy band diagram for the molecular junctions prepared and therefore are not able to distinguish between different electron transport mechanisms. In my talk, I will present new I(V,T) and IETS results obtained from a Au-S-C8H16-S-Au junction, which give insight into these questions. I will also discuss a new planar device structure developed at Yale and the utilization of electrochemistry as a quality monitor in molecular electronics.

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New materials will be necessary to break through todays performance envelopes for solid-state energy conversion devices...
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New materials will be necessary to break through todays performance envelopes for solid-state energy conversion devices ranging from LED-based solid-state white lamps to thermoelectric devices for solid-state refrigeration and electric power generation. The combination of recent materials advances and development of practical bottom-up nanofabrication methods offers to provide the degrees of freedom necessary to design practical nanocomposite-based devices that can eclipse the performance of conventional thin-film or bulk devices. Relaxation of elastic mismatch strain at free surfaces in semiconductor nanorods and nanowires allows the accommodation of a broader range of lattice mismatch and band-lineups in coherent nanostructures than is possible in thin-film heterostructures. This new space for bandgap engineering provides the opportunity to confine and manipulate electrons, phonons and photons at scales that are comparable to their characteristic wavelengths and scattering lengths. Likewise, nanorod, nanowire and multilayer nanocomposites intimately combine materials with disparate functionalities to create fundamentally new materials that do not resemble the constituent materials in their transport properties, anisotropy or crystal structures. In this talk, I will illustrate these new opportunities with our recent work in the design of monolithic phosphor-free white light emitters based on nanorod heterostructures, and metal/semiconductor solid-state thermionic energy converters utilize.

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Thermoelectric effects are based on the difference between the average energy of the conduction electrons (or holes) and the...
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Thermoelectric effects are based on the difference between the average energy of the conduction electrons (or holes) and the Fermi energy. A thermoelectric material can be configured into a device for solid-state refrigeration or electrical power generation. Although these devices are presently restricted to niche applications - including beverage coolers, temperature control of communications lasers, and radioisotope thermoelectric generators for deep space probes âthere is great potential for widespread application if the materials can be improved. In particular, an increase in the materialsâ dimensionless figure-of-merit, ZT, from todayâs values of ~1 to values above 4 would enable replacement of compressor based refrigeration with a solid-state alternative. Applications such as conversion of waste heat from vehicle exhaust to electric power would also become feasible. The key to designinghigh ZT materials is to manipulate phonons and electrons at the nanoscale. Confining electrons and holes can enhance the numerator of ZT, known as the power factor. Introducing defects that scatter phonons but not electrons can decrease the thermal conductivity (the denominator of ZT) without appreciably affecting the power factor. In this tutorial, I will review recent strategies for designing high-ZT nanostructured materials, including superlattices, embedded quantum dots, and nanowire composites. The challenges inherent to coupled electronic and thermal transport properties will be highlighted.

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Recent demonstrations of high performance carbon nanotube field-effect transistors (CNFETs) highlight their potential for a...
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Recent demonstrations of high performance carbon nanotube field-effect transistors (CNFETs) highlight their potential for a future nanotube-based electronics. Besides being just a nanometer in diameter, carbon nanotubes offer intrinsic advantages if compared with silicon that are responsible for their outstanding properties. Their one-dimensional character is advantageous for a low scattering probability and consequently a high on-current in a transistor device. Electrons and holes behave similarly in CNs, enabling a complementary metal-oxide semiconductor (CMOS) like technology with n-type and p-type transistors. Since chemical bonds in case of carbon nanotubes are completely satisfied, problems with dangling bonds, as at any silicon surface, do not exist. This implies that carbon nanotubes can be more easily combined with various gate dielectrics, e.g. high-k dielectrics for an improved gate control. And last, the fact that metallic as well as semiconducting carbon nanotubes can be fabricated may lead to an all nanotube-based electronics with metallic tubes acting as interconnects and semiconducting tubes being used as active device regions.All of the above aspects of nanotubes have been experimentally verified. Investigating the physics of scaled CNFETs however revealed also a number of other - rather unexpected - properties of nanotube-based devices. The most important and far-reaching observation recently made is that CNFETs are indeed Schottky barrier devices. This has important implications for their scaling behavior as well as their performance limits. In my presentation I will focus in particular on this aspect of carbon nanotube transistors and discuss a number of our most recent experimental data and simulations.

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Characterization of charge transport in molecular scale electronic devices has to date shown exquisite sensitivity to...
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Characterization of charge transport in molecular scale electronic devices has to date shown exquisite sensitivity to specifics of device fabrication and preparation. Thus, intrinsic molecular band structure has been problematic to extract from published results. Here we demonstrate cross-platform device characterization for the metal-insulator-metal (M-I-M) tunneling through a large bandgap alkanethiol self-assembled monolayers (SAMs).Electronic charge transport is investigated for various-length alkanethiol SAMs using three different characterization methods, in which lateral areas span the nanometer to the micrometer scale. In each method, the measured current-voltage characteristics are analyzed with metal-insulator-metal tunneling models. Transport parameters are determined where possible and compared across methods, as well as to previously reported values. Advantages and limitations of these various methods for characterizing molecular junctions are briefly discussed.We also perform inelastic electron tunneling spectroscopy (IETS) on alkanedithiol nanoscale devices. The IETS spectrum of the octanedithiol device clearly shows vibrational signatures of an octanedithiolate bonded to gold electrodes. The pronounced IETS peaks correspond to vibrational modes perpendicular to the junction interface, which include the Au-S and C-C stretching modes and CH2 wagging mode. The observed peak intensities and peak widths are in good agreement with theoretical predictions.

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SFRE 199-1 medium (SFRE-M) is important mammalian cell culture medium, used for the culture of primary cells of mammals such...
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SFRE 199-1 medium (SFRE-M) is important mammalian cell culture medium, used for the culture of primary cells of mammals such as baboon kidney cells. The present study was attempted to evaluate the impact of biofield energy treatment on the physical, thermal and spectral properties of SFRE-M. The study was accomplished in two groups; one was set as control while another was subjected to Mr. Trivedi’s biofield energy treatment and coded as treated group. Subsequently, the control and treated samples were analyzed using various analytical techniques. The CHNO analysis showed about 2.16, 4.87, and 5.89% decrease in percent contents of carbon, hydrogen, and oxygen, respectively; while 9.49% increase in nitrogen contents of treated sample as compared to the control. X-ray diffraction (XRD) analysis showed 7.23% decrease in crystallite size of treated sample as compared to the control. The thermogravimetric analysis (TGA) analysis showed the increase in onset temperature of thermal degradation by 19.61% in treated sample with respect to the control. The control sample showed the 48.63% weight loss during the thermal degradation temperature (Tmax) while the treated sample showed only 13.62% weight loss during the Tmax. The differential scanning calorimetry (DSC) analysis showed the 62.58% increase in the latent heat of fusion of treated sample with respect to the control sample. The Fourier transform infrared spectroscopy (FT-IR) spectrum of treated SFRE-M showed the alteration in the wavenumber of C-O, C-N and C-H vibrations in the treated sample as compared to the control. Altogether, the XRD, TGA-DTG, DSC, and FT-IR analysis suggest that Mr. Trivedi’s biofield energy treatment has the impact on physical, thermal and spectral properties of SFRE-M. The treated SFRE-M was more thermal stable than the control SFRE-M and can be used as the better culture media for mammalian cell culture.

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The quantitativelly accurate prediction of materials behavior from first principles requires the chracterization of a wide...
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The quantitativelly accurate prediction of materials behavior from first principles requires the chracterization of a wide range of phenomena with disparate temporal and spatial scales form electrons and atoms to devices. No single theory of computational model can capture all these phenomena with the required level of accuracy; thus, a multi-scale, multi-physics approach involving a combination of theories and computational techniquesis necessary. This tutorial will describe some of the most powerful and widely used techniques for materials modeling including i) first principles quantum mechanics (QM), ii) large-scale molecular dynamics (MD) simulations and iii) mesoscale modeling together with the strategies to bridge between them. I will also exemplify the use of these computational techniques to characterize mechanical, chemical, and structural properties of a variety of materials, from metals to energetic materials. Being based on first principles, the techniques and strategy described here are predictive and should be useful to help guide the design and optimization of new materials or devices with improved properties.

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